Device and method for detecting a divergence of an adaptive system and use of such a device for the detection of a divergence of a digital filter

Abstract

A divergence detection device for an adaptive system comprising means for calculating the energy of an input signal of the system, means for calculating the energy of an output signal of the system and means for analysing the energy of the input signal and the energy of the output signal so as to detect a rise in the energy of the output signal, relative to the energy of the input signal, in case of divergence of the system.

1. A divergence detection device for an adaptive system including a filter, the divergence detection device comprising:
 means for calculating the energy of an input signal of the filter, means for calculating the energy of an output signal of the filter, 
 means for analysing the energy of the input signal and of the output signal so as to detect a rise in the energy of the output signal, relative to the energy of the input signal, in case of divergence of the adaptive system, 
 means for calculating a ratio between the energy of the output signal and the energy of the input signal, 
 means of comparison for comparing the ratio calculated with a threshold value corresponding to a divergence of the adaptive system, 
 means for resetting coefficients of the filter to zero or for restoring the coefficients to a state corresponding to a convergence, when the ratio between the energy of the output signal and the energy of the input signal is greater than the threshold value, 
 means for counting up/down intended to be incremented and decremented as a function of the results of the comparison carried out by the means of comparison, and 
 means for comparing a count value of the up/down counter with a divergence detection threshold value. 
 
     
     
       2. A method of detecting a divergence of an adaptive system including a filter, the method comprising the steps:
 calculating the energy of an input signal of the filter and the energy of an output signal of the filter; and 
 analysing the energy of the input signal and of the output signal so as to detect a rise in the energy of the output signal, relative to the energy of the input signal, in case of divergence, wherein the analysis includes:
 calculating a ratio between the energy of the output signal and the energy of the input signal, 
 comparing the ratio with a threshold value, 
 resetting coefficients of the filter to zero or restoring the coefficients to a state corresponding to a convergence, when the ratio between the energy of the output signal and the energy of the input signal is greater than the threshold value, 
 incrementing or decrementing an up/down counter as a function of the results of the comparison, and 
 comparing a count value of the up/down counter with a divergence detection threshold value. 
 
 
     
     
       3. The method according to  claim 2 , wherein the counter is incremented if the ratio is greater than a first threshold value corresponding to a divergence of the system. 
     
     
       4. The method according to  claim 2 , wherein the counter is decremented if the ratio is less than the threshold value. 
     
     
       5. The method according to  claim 2 , wherein the count value of the up/down counter is moreover compared with a second divergence detection threshold value. 
     
     
       6. The method according to  claim 2 , wherein the first threshold value is a fixed threshold value. 
     
     
       7. The method according to  claim 2 , wherein the first threshold value is variable. 
     
     
       8. The method according to  claim 2 , wherein the said method is adapted for the detection of a divergence of an adaptive filter of an echo canceller of a telecommunications facility, of a system implementing a predictive algorithm or a recursive digital filter.